Crystalline electric fields in mixed valent systems
The inelastic neutron studies of rare-earth-based mixed valent systems have all shown remarkably similar results: a broad quasielastic line with half width on the order of 10 MeV. This width exhibits a strong temperature dependence in those systems which undergo a valence transition and is only weakly temperature dependent in those systems which show no transition. A surprising result was the absence of crystalline electric field (CEF) excitations. Recent measurements on the alloy Ce/sub .9-x/La/sub x/Th/sub .1/ have revealed the existence of CEF excitations. For x = 0, the valence transition is strongly first order and occurs near T/sub 0/ approx. 150 K. The inelastic spectra exhibit the typical broad quasielastic scattering. As x increases, T/sub 0/ decreases due to internal pressure effects, and a well-defined, but broad, excitation appears near E = 15 MeV. This is interpreted as a CEF excitation between the GAMMA/sub 7/ and GAMMA/sub 8/ levels of the Ce/sup 3/+ ion. For x = 0.40, the valence transition is almost completely suppressed and the excitation becomes even sharper.
- Research Organization:
- Brookhaven National Lab., Upton, NY (USA)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 6768928
- Report Number(s):
- BNL-28632; CONF-801134-11; TRN: 81-000982
- Resource Relation:
- Conference: 26. annual conference on magnetism and magnetic metals, Dallas, TX, USA, 11 Nov 1980
- Country of Publication:
- United States
- Language:
- English
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